一.情态动词need：need只有在疑问句和否定句中可用作情态动词，表示“需要”：
Need we answer this letter?
这封信我们需要回吗?
So I needn't tell him，need I?
所以我无需告诉他，对吧?
We needn't worry.
我们无需发愁。
You needn't have mentioned it.
这事你是不必提到的。
—Need I come?
一Yes，you must?
—我需要来吗?
一你一定要来。
need也可用作及物动词，这时可和不定式连用，可用于肯定句、疑问句和否定句：
We need to make preparations.
我们需要作准备。
Does she need to be notified?
需要通知她吗?
You don't need to do it yourself.
这事你不必亲自去做。
二.情态动词dare：dare只在极少数情况下用作情态动词，主要用在疑问句、否定句及条件从句中，表示“敢”：
Dare you go home alone?
你敢一个人回家吗?
She daren't even look at me.
她甚至不敢看我。
How dared they do such a thing?
他们怎么敢干这样的事?
No one dared speak of it.
没人敢谈起这件事。
I won't allow you to do it even if you dare do it.
就是你敢做我也不让你这样做。
在多数情况下dare都用作及物动词，和带to的不定式一起用：
We must dare to act.
我们要敢干。
The girl did not dare to go home alone.
这姑娘不敢一个人回家。
No one dared to suspect him.
没人敢怀疑是他。
Who dares to jump over the stream?
谁敢跳过小溪?
